
interface USB {
    void start();
    void stop();
}

class C {
    public static void work(USB u) {
        u.start();
        System.out.println("工作中");
        u.stop();
    }
}

class USBDisk implements USB {

    @Override
    public void start() {
        System.out.println("U盘开始工作");
    }

    @Override
    public void stop() {
        System.out.println("U盘停止工作");
    }
}

public class InterDemo01 {
    public static void main(String[] args) {
//        System.out.println("Hello World!");
        C.work(new USBDisk());
    }
}
